Could a water bubble (spherical occlusion of water in air or vacuum) similar to the one in the picture below remain in Earth orbit without evaporating, dispersing, or disintegrating? Assume the orbit is high enough (high LEO or MEO) so that re-entry is not the limiting factor.

  • Is there a range of sizes that would be suitable; is there a "too small" or "too large" to remain stable?
  • Would it likely remain liquid, or would it freeze?
  • Assuming the water was originally pure and potable, would it eventually become toxic or unsuitable for drinking as a result of being in Earth orbit?

If a time limit is necessary for the answer, let's say we'd like it to remain stable, and ideally drinkable, for 100 years.

enter image description here

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    $\begingroup$ Reference: Roche limit of fluid satellites, Project Highwater $\endgroup$ Nov 20, 2018 at 23:18
  • $\begingroup$ @RussellBorogove those tests produce nice spheres of water, or destructively disperse the water into lots of little ones? $\endgroup$
    – uhoh
    Nov 21, 2018 at 2:07
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    $\begingroup$ I've added some to your question to give some specific technical details. I think this is a great question! $\endgroup$
    – uhoh
    Nov 21, 2018 at 4:08

1 Answer 1


The ball of water in that picture is in orbit; it's just surrounded by (presumably) the ISS.

But a ball of water like that definitely cannot survive in the vacuum of space. Below a certain pressure, water can only be water vapor or ice. So a ball like that would immediately start to boil if it were surrounded by a vacuum. The water vapor would quickly disperse and there would be nothing there.

It would not become toxic. If it were kept in a container to keep it from evaporating, it would just be water.

A giant, moon-sized ball of water is a whole different story. Gravity would hold it together. There would be an atmosphere of water vapor above an ocean of water that extended all the way through. In the middle, the pressure would be so great that its properties would change. [Note added later: After writing this I believe I read that the pressure at the center of a Moon-sized ball of water would not be great enough to lead to one of the special kinds of ice that exist at high pressures. So its properties might not actually change.]

This is all assuming it's close enough to the sun to remain liquid. Some of the moons in the outer solar system are mostly ice, and at least Enceladus (around Saturn) and Europa (around Jupiter) have large oceans under the ice.

  • $\begingroup$ A solid tennis ball sized piece of ice would boil also, right? $\endgroup$ Dec 23, 2018 at 21:22
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    $\begingroup$ @MagicOctopusUrn Well, it would sublime. That is, it would go directly from ice to vapor. $\endgroup$ Dec 24, 2018 at 2:50
  • $\begingroup$ As long as the ball of of water is solid it will not boil. Depending on environment pressure and temperature it will either sublimate (change directly from ice to vapor) or melt from solid ice to liquid water. If the liquid water is heated, it mayy boil eventually. $\endgroup$
    – Uwe
    Dec 24, 2018 at 15:45

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